A. Ethylene terephthalate/PEG terephthalate soil release polyesters used in laundry detergent compositions
U.S. Pat. No. 4,116,885 to Derstadt et al., issued Sept. 26, 1978, discloses laundry detergent compositions containing 0.15 to 25% (most preferably 0.5 to 10%) of an ethylene terephthalate/PEG terephthalate soil release polyester, such as MILEASE T, having an average molecular weight of 5000 to 200,000 (preferably 10,000 to 50,000). These detergent compositions further contain 5 to 95% (most preferably 10 to 25%) of certain compatible alcohol sulfate and alkylethoxy sulfate detergent surfactants and no more than 10% of other incompatible anionic surfactants such as the linear alkyl benzene sulfonates.
U.S. Pat. No. 4,132,680 to Nicol issued Jan. 2, 1979, also discloses laundry detergent compositions having soil release properties which contain 2 to 95% (preferably 10 to 60%) of a detergent surfactant and 0.15 to 25% (most preferably 1 to 10%) of an ethylene terephthalate/PEG terephthalate (mole ratio of 65:35 to 80:20) soil release polyester having a molecular weight of 10,000 to 50,000, e.g. MILEASE T. These compositions further comprise 0.05 to 15% (most preferably 0.1 to 5%) of a component which disassociates in aqueous solution to yield quaternary ammonium cations having one to three C.sub.8 -C.sub.24 alkyl groups. These cations are taught by Nicol to improve the deposition of the soil release polyester on the laundered fabric. See column 11, lines 14-21.